1. Field of the Invention
The present invention relates to a photosensor for detecting the focus, a focus detecting device, and an image pickup apparatus.
2. Description of the Related Art
When the focus of an object at the same distance is detected with a phase-difference focus detecting device, the focus detection result varies (defocusing) in accordance with the wavelength because of chromatic aberration of an imaging optical system.
For this focus detecting device in which the focus detection result varies, for example, Japanese Patent Publication No. 1-45883 proposes a technique of detecting and correcting the variation in the focus detection result due to the difference of the light source by using a light-receiving section that detects the light source. In this focus detecting device, a signal corresponding to the infrared region and signals of other wavelength regions are detected, the defocus amount is calculated, and defocusing is corrected on the basis of the defocus amount.
Japanese Patent No. 2555681 proposes a focus detecting device in which first and second photodiodes for detecting the color temperature are disposed adjacent to a base portion and a reference portion of a focus-detecting photodiode array on the same chip. In this focus detecting device, the photodiode array and the first and second photodiodes receive almost the same object image.
Japanese Patent Laid-Open No. 2004-272238 discloses a focus detecting device in which a plurality of focus-detecting photoreceptors are provided corresponding to a plurality of optical systems and in which monitoring photoreceptors are provided adjacent to the focus-detecting photoreceptors.
In the technique disclosed in Japanese Patent Publication No. 1-45883, a photoreceptor that obtains a photoelectric signal indicating infrared light and a photoreceptor that obtains a photoelectric signal indicating light with other wavelengths are provided near photoreceptors that detect the focus of a light beam received from an imaging optical system that forms an object image. However, this publication does not describe the arrangement of the photoreceptors for a plurality of focus detecting fields. Japanese Patent 2555681 teaches that the photodiodes for detecting the color temperature are provided adjacent to the photodiode array, but does not describe the arrangement for a plurality of focus detecting fields.
In the focus detecting device disclosed in Japanese Patent Laid-Open No. 2004-272238, a monitoring photoreceptor is provided for each focus detecting photoreceptor. However, with the increase in number of distance measuring fields of the focus detecting device, the number of focus-detecting photoreceptors increases, and the number of monitoring photoreceptors increases in proportion thereto. Consequently, the sizes of the sensor circuit and the sensor are increased.